1. Field of the Disclosure
The present invention relates generally to power supplies and, more particularly, the present invention relates to forward converters.
2. Background
AC-to-DC and DC-to-DC power supplies typically use a power conversion topology commonly known as a two-switch forward converter (that is, a forward converter having two active switches).
The two-switch forward converter typically uses two active switches and two passive switches in a configuration that applies an input voltage to the primary winding of a transformer. A secondary winding on the transformer produces a scaled voltage in response to the input voltage applied to the primary winding. The voltage on the secondary winding is rectified and filtered to generate an output voltage. The passive switches allow the magnetizing energy of the transformer to reset when the active switches are off. The magnetizing energy of the transformer is allowed to reset (that is, return to a much lower value) to prevent excess stored energy from saturating the transformer and thereby altering its properties.
The two-switch forward converter is often the lowest cost configuration that meets the requirements of power supplies for personal computers and similar applications. The symmetry of the circuit topology of the two-switch forward converter invites designers to choose nominally identical transistors for the two active switches and to choose nominally identical diodes for the two passive switches.
Conventional designs of two-switch forward converters specify either the same component or two different components with nearly identical properties for the two transistors, and likewise for the two diodes. Such designs fail to take advantage of an additional degree of freedom that can reduce system cost.